I’m taking a deep travel across Vala code; trying to figure out how things work. With my resent work on abstract methods for compact classes, may I have an idea on how to provide ABI stability to GXml.
GXml have lot of interfaces for DOM4, implemented in classes, like Gom* series. But they are a lot, so go for each and add annotations, like Gee did, to improve ABI, is a hard work.
I think is better to improve Vala code to produce ABI stability from the beginning; this will help GXml, GSVG (implementing W3C SVG 1.1 interfaces) and GSVGtk, to have abstract classes and interfaces with good ABI stability without change a line of code in them.
In the process, we can have reproducible API, that is: same C header from compilation to compilation of Vala code and when you add new API. Of course, this means that you should follow basic rules when write Vala code, but no more than the ones on the C side, well may be a few ones. When this is in place, you may add your library header to your repository to track changes to it; once a new API has been added, you should be able to take care about ABI and API, to make sure they are consistent over time.